1. Field of the Invention
This invention relates to a winch and more particularly to an improvement in the operating components of an existing prior art winch.
2. Description of the Prior Art
The most relevant prior art known to the applicant herein is a winch manufactured by Warn Industries, Inc. of Kent, Wash., the assignee of the present invention. That winch comprises a motor which transmits power through a speed reducing gear transmission to a first drive cam having an axially facing cam surface which engages an axially facing cam face of a second driven cam which through a further speed reducing transmission drives the cable winding drum of the winch. A clutch-brake assembly is operatively connected between the two cams, this assembly comprising a first shoe connected to the first cam to rotate therewith, a second shoe connected to the second cam to rotate therewith, and a ratchet plate positioned between the two shoes. There is a pawl which can be moved by an operating lever into and out of engagement with the ratchet plate. When the pawl is disengaged, the ratchet plate can move freely in either direction, and when the pawl is engaged, the ratchet plate can move only in the direction which the brake-clutch assembly rotates in reel in cable.
When the winch is operating under power in either direction, e.g. in raising or lowering a load, the pawl is positioned to be in engagement with the ratchet plate. When the winch is operated in a first direction to reel cable in, the drive cam engages the driven cam in wedging engagement to tend to move the two cams axially away from each other and to push the two shoes into engagement with the ratchet plate. This effectively locks up the two cams and the clutch assembly in a single rotating unit through which power is transmitted to the drum.
When the winch is operated in the opposite direction, e.g. in lowering a load, the drive cam moves in a direction out of wedging engagement with the second cam, so that it does not push the shoes of the brake-clutch assembly into engagement with the ratchet plate. However, a circumferentially facing shoulder of the drive cam engages a matching shoulder of the driven cam so that the driven cam is positively engaged to be moved in a direction to unwind cable. If the cable is under tension loading as in the instance of lowering a suspended mass, the tension load on the cable tends to cause the second driven cam to overrun the first drive cam to push the drive cam back into wedging engagement. Since the pawl in its engaged position does not permit rotation of the ratchet plate in a direction to unwind cable, as the two shoes come into frictional engagement with the ratchet plate, the ratchet plate acts as a governor to limit the rotational speed of the components to that which the motor imparts to them. When the winch motor is stopped, any tension loading on the cable moves the clutch-brake assembly into engagement to prevent the cable from unreeling. In this instance the clutch-brake assembly functions as a brake on the drum.
In the event that it is desired to unwind the winch cable at a relatively fast rate, the operating lever of the pawl is manipulated to move the pawl to its disengaged position, so that the ratchet plate is free to move in either direction. In this situation, the cable can be pulled out relatively easily, with the only restraining force being the internal drag of the operating components of the winch. However, after the cable is pulled out, the pawl must be moved back to its engaged position so that the clutch-brake assembly can perform its intended functions as indicated above.
While the above-described winch operates satisfactorily, it is possible for the careless operator to disregard the usual safety precautions in the improper operation of the winch. For example, with the winch mounted to the front bumper of a vehicle, the vehicle operator sometimes uses the winch as an auxiliary power source to travel very rugged terrain. To travel up a very steep hill, the operator sometimes takes the end of the cable and climbs up the hillside to attach the free end of the cable to a tree or other stationary object, with the brake pawl being disengaged so that the cable pays out more quickly as the operator moves away from the vehicle. The operator then returns to his vehicle and should engage the pawl, after which he turns on the winch motor to reel in cable so that the vehicle with the winch pulls itself up the incline, with or without assistance from the drive wheels of the vehicle. After reaching the desired level up the incline, the operator stops the winch motor, and with the brake pawl engaged the winch will hold the cable drum at its present position. If desired, the motor can be placed in reverse at a later time and the vehicle descends the hill at a controlled rate. However, if the operator neglects to engage the pawl, when the winch motor is stopped, only the internal drag of the operating components of the winch prevents the free paying out of cable. The rather substantial weight of the vehicle overcomes this relatively small retarding force, and the vehicle unfortunately descends the hill at a rate faster than that desired by the operator, even with the operator applying the wheel brakes of the vehicle in those instances where the incline is quite steep.
Another situation is that where an operator of a vehicle having a winch thereon wishes to lower himself into a ravine with the assistance of the winch. The operator parks the car near the edge of the ravine, secures himself to the end of the cable, starts the winch motor in a direction to pay out cable, and then steps over the edge of the ravine with the expectation that the controlled rate of paying out cable by the winch will provide a comfortably slow descent. However, unless the operator has taken the usual care to be sure the pawl is engaged, the drum is able to overrun the motor with the operator making the descent down the ravine at a rate somewhat faster than the operator had initially planned.
A possible solution to this problem is to modify the brake-clutch assembly so that it cannot freely rotate in a direction to pay out cable. However, this limits the rate at which cable can be payed out to the speed at which the winch can operate. Since the winch is usually geared for a high torque-low speed setting, this has the disadvantage of imposing an undesired limitation on the speed with which the cable can be unreeled from the drum. Consequently it sometimes leads to the operator tampering with the brake-clutch assembly to disengage it and permit the cable to pay out freely, which impairs the safe operation of the winch.
Another possible solution is to provide some sort of interlock between the motor and the pawl, so that the winch cannot operate under power unless the pawl is engaged. While this proposed solution does have merit, it leads to a more complex apparatus, and the addition of such complexities inherently produces further problems of reliability, as well as added expense, maintenance, etc.
Thus, it is an object of the present invention to provide an improvement to a winch such as that described above, to improve the operating characteristics of the winch with regard to the considerations discussed above.